1. Field of the Invention
This invention relates generally to hybrid electric vehicles, and more particularly to a control strategy for a hybrid electric vehicle of the type in which a dynamoelectric machine, such as a combination starter/alternator, interacts with a combustion engine that drives road-engaging wheels through a drivetrain.
2. Background Information
In one type of hybrid electric vehicle (HEV) a combustion engine is coupled through a drivetrain to road-engaging wheels, and a dynamoelectric machine, such as a combination starter/alternator, can interact with the engine either to add to or to subtract from the torque output of the engine into the drivetrain. Such a starter/alternator may be structurally integrated with a combustion engine.
At some times, the dynamoelectric machine may develop torque that is additive to the engine torque, thereby augmenting the torque from the engine into the drivetrain, while at others, it may instead impose a torque load on the engine, diminishing the magnitude of torque that can be delivered by the engine into the drivetrain. In other words, when it is adding to the engine torque into the drivetrain, the dynamoelectric machine functions as an electric motor, and when it is subtracting from the engine torque into the drivetrain, it functions as an alternator, or electric generator, that is being driven by the engine.
When functioning as an alternator powered by the engine, the rotating electric machine generates electricity that can be used for any appropriate purpose, such as charging an on-board storage battery, or batteries. When functioning as a motor, the rotating electric machine may draw electric current from the storage battery, or batteries, to supplement the power output of the engine to the drivetrain.
In order to conserve energy during times when it is idling, the engine may instead be shut down temporarily until it is once again called on to deliver torque to the drivetrain. Because of its association with the combustion engine, the electric machine may be used as a motor, drawing power from the on-board battery, or batteries, to re-start the engine.
From the foregoing brief and somewhat general description, it can be understood that various possible modes in which a rotating electric machine can interact with a combustion engine require a sophisticated control system and control strategy. The availability of high-speed electronic devices, such as processors, enables sophisticated control strategies to be implemented in real time. For example, a basic control system may comprise a processor-based starter/alternator (S/A) controller and a processor-based engine controller. For control of certain interactions between the starter/alternator and the engine toward achieving a desired operational result, it may be necessary for required data to be transmitted between sensors and controllers and/or between controllers in real time. Such a data transfer requirement may overload an existing data communication link, and therefore in order to accommodate the data transfer requirement, the data communication link may have to be expanded, making implementation of the desired control strategy either very expensive or simply impossible. It would therefore be beneficial if a desired control strategy that would avoid both of those alternatives could be realized.
U.S. Pat. Nos. 4,335,429; 4,922,869; 5,176,213; 5,327,992; 5,656,921; 5,833,570 and 5,839,533 were developed in consequence of a novelty search with respect to the present invention, and they are believed representative of the state of the art. They disclose various forms of HEV""s and control systems. Certain control systems shown in those patents contain maps for use in various control strategies.
The present invention relates to improvements in HEV control strategy implementation, particularly in an HEV of the type discussed above where a dynamoelectric machine is arranged for interaction with a combustion engine so as to function, with respect to the engine, at times as a power source, i.e. as an electric motor, for adding torque into the drivetrain, and at times as a power sink, i.e. as an alternator, for replenishing the charge of an on-board storage battery. This type of HEV is representative of what is sometimes referred to as a low storage requirement HEV.
For achieving a desired operational result by real-time control of interaction between a dynamoelectric machine and a combustion engine in an HEV, the invention provides an alternative solution to one that merely expands an existing data communication link in order to accommodate real time transfer of data required for implementation of a desired control strategy that is needed in order to achieve the desired operational result. The solution provided by the present invention is believed preferable because it may avoid the added cost which might be imposed on an HEV by expanding an existing data communication link for the sole purpose of implementing a particular desired control strategy.
Briefly, one aspect of the present invention relates to a control strategy where certain aspects of engine operation are mapped, the maps are stored in a controller for the dynamoelectric machine, i.e. an S/A controller, and the stored maps are utilized by the S/A controller during HEV operation to cause the starter/alternator to quickly respond to changing variables so that a desired operational result is achieved without having to rely on the engine controller or the vehicle system controller.
More especially, one general aspect of the invention relates to a hybrid electric vehicle comprising: a powerplant for propelling the vehicle comprising a combustion engine and a dynamoelectric machine; a control system comprising a vehicle controller that receives driver input and issues respective outputs to an engine controller for controlling the engine and to a dynamoelectric machine controller for controlling the dynamoelectric machine, respectively; a signal source on the engine providing engine speed data to said dynamoelectric machine controller; the dynamoelectric machine controller comprising a look-up table that contains respective make-up torque values correlated with respective values of engine speed data; and the dynamoelectric machine controller comprising a processor that causes a make-up torque value from the look-up table corresponding to a value of engine speed data received from the signal source, to be included in the torque output of the dynamoelectric machine.
Another general aspect relates to a hybrid electric vehicle comprising: a powerplant for propelling the vehicle comprising a combustion engine having a crankshaft and a dynamoelectric machine; a control system comprising a vehicle controller that receives driver inputs and issues respective outputs to an engine controller for controlling the engine and to a dynamoelectric machine controller for controlling the dynamoelectric machine, respectively; a signal source on the engine providing engine crankshaft position information to said dynamoelectric machine controller; the dynamoelectric machine controller comprising a stored make-up torque profile correlated with crankshaft position for attenuating pulsations in engine torque output induced by changing pressures in combustion cylinders of the engine as the engine crankshaft rotates; and the dynamoelectric machine controller comprising a processor that causes make-up torque corresponding to the stored profile to be included in the torque output of the dynamoelectric machine in attenuating relationship to pulsations in engine torque output induced by the changing pressures in the combustion cylinders of the engine as the engine crankshaft rotates.
Another general aspect relates to a hybrid electric vehicle comprising: a powerplant for propelling the vehicle comprising a combustion engine and a dynamoelectric machine; a control system comprising a vehicle controller that receives driver input and issues respective outputs to an engine controller for controlling the engine and to a dynamoelectric machine controller for controlling the dynamoelectric machine, respectively; a signal source on the engine providing data related to crankshaft motion, said data provided to said dynamoelectric machine controller; a data communication link from the signal source to the dynamoelectric machine controller via which the crankshaft motion data is communicated to the dynamoelectric machine controller; the dynamoelectric machine controller comprising at least one look-up table for developing a respective makeup torque value correlated with the crankshaft motion data and data for at least one other variable related to vehicle operation; and the dynamoelectric machine controller comprising a processor that causes a make-up torque value from the at least one look-up table to be included in the torque output of the dynamoelectric machine in accordance with the crankshaft motion data and the at least one other variable data.
Still another general aspect relates to a method of operating a hybrid electric vehicle of the type comprising a powerplant for propelling the vehicle comprising a combustion engine having a crankshaft and a dynamoelectric machine; a control system comprising a vehicle controller that receives driver inputs and issues respective outputs to an engine controller for controlling the engine and to a dynamoelectric machine controller for controlling the dynamoelectric machine, respectively; the method comprising: supplying engine speed data from a signal source on the engine to the dynamoelectric machine controller; operating a processor of the dynamoelectric machine controller to look up make-up torque values that are stored in the dynamoelectric machine controller in correlation with respective values of engine speed data; and outputting from the processor make-up torque signals correlated to values of supplied engine speed data to create make-up current in the dynamoelectric machine that contributes to the torque output of the dynamoelectric machine in an amount corresponding to looked-up make-up torque.
Further aspects will be seen in the ensuing description, claims, and accompanying drawings.